As a result of the very low sulfur concentration specifications for diesel fuels, there has been a great effort by those in industry to find new hydrotreating catalyst formulations and products that may be used in the manufacture of low-sulfur diesel and other products.
One catalyst taught by the art for use in the hydrotreating of certain hydrocarbon feedstocks so as to meet some of the more stringent sulfur regulations is disclosed in U.S. Pat. No. 5,338,717. In this patent, a hydrotreating catalyst is disclosed that is made by impregnating a Group VI (Mo and/or W) heteropolyacid onto a support followed by treating the impregnated support with an aqueous solution of a reducing agent that may be dried and thereafter impregnated with a Group VIII (Co and/or Ni) metal salt of an acid having an acidity of less than that of the Group VI heteropolyacid. This impregnated support is then dried and sulfided to provide a final catalyst.
The catalyst composition disclosed in the '717 patent may also be made by impregnating a support with both the Group VIII metal salt and the Group VI heteropolyacid followed by drying and then treating with a reducing agent, drying again, and sulfiding to form the final catalyst.
Another catalyst useful in the deep hydrodesulfurization and in other methods of hydrotreating hydrocarbon feedstocks and a method of making such catalyst and its activation are disclosed in U.S. Pat. No. 6,872,678. The catalyst of the '678 patent includes a carrier upon which a Group VIB hydrogenation metal component and/or a Group VIII hydrogenation metal component and a sulfur-containing organic compound additive are incorporated and further which has been contacted with a petroleum fraction organic liquid. The catalyst is treated with hydrogen either simultaneously with or after the incorporation of the organic liquid (petroleum fraction).
U.S. Pat. No. 8,262,905 discloses a composition that is particularly useful in the catalytic hydroprocessing of hydrocarbon feedstocks. One composition disclosed in the '905 patent includes a support material that is loaded with either an active metal precursor or a metal component of a metal salt, and hydrocarbon oil and a polar additive. The polar additive has a dipole moment of at least 0.45 and the weight ratio of hydrocarbon oil to polar additive in the composition is in the range of upwardly to 10:1. It is particularly desirable for the polar additive to be a heterocompound except those heterocompounds that include sulfur. The most preferred polar additive compounds are selected from the group of amide compounds.
U.S. Pat. No. 6,540,908 discloses a process for preparing a sulfided hydrotreating catalyst. This process involves combining a catalyst carrier of alumina and a hydrogenation metal catalyst carrier with an organic compound that includes a covalently bonded nitrogen atom and a carbonyl moiety followed by sulfiding the resulting combination. The '908 patent does not explicitly teach or exemplify that its organic compound can include a heterocyclic compound. A preferred organic compound is indicated to be one that satisfies the formula (R1R2)N—R3—N(R1′R2′).